2. What are some of the "weird" things about human beings? How does this cause a need for anthropologists?

the following key ideas correctly express the key sentence.

restate key idea: most people can learn to swim in ten short lessons.

restate key idea: the majority of water-accident victims require mouth-to-mouth breathing.

restate key idea: an empty, tightly closed gallon jug will support a tired swimmer.  

restate key idea: first aid is to prevent accidents as well as assist in rescue.

explanation: the key idea needs to have the same topic as the key sentence (drowning and safety).

"the sandy walls seemed to collapse in on themselves"

and

"the bloodshot waters seemed to have no bottom"

i think that it is (line 11)